Overheating/coolant boiling after coolant change and bleed

[Gasy]

As said see saw method
And give it a few vroom vroom revs on the accelerator
You will see it burp some more bubbles when you vroom vroom the accelerator peddle a few times

Watch them vids again if you have
It's easy to forget things

[Northern Bongolow]

water wetter will get you about 3-4 degrees drop, it did on the bongo i tried it on, better to sort it than mask it i think.

another thing it could be is the cap on the expansion tank, i made a cap tester out of an old expansion tank with a pressure gauge fitted so i could read when the cap let go with a squeak, more than half of those i test fail. they open early so drop pressure which lowers the boiling point of the coolant.

i fitted a coolant pressure gauge monitor on my bongo and made the following observations.

the average bongo runs at around 8-9 pounds internal positive pressure when warmed up, working hard is a tad higher, the fans come on first slow speed at about 13 pounds, then second speed above that. this leaves a narrow margin to 1.1 bar where a good new cap blows off at, a faulty cap that blows early or one that blows early then stays open for longer than it should would let your bongo boil.

your front rad is in good condition isnt it ??. they can start to come apart at the 2 seams, one top the other bottom where the metal crimps to the plastic, look for coolant coloured stains, has it got an open pipe at the side of the rad cap ??.

[Lordward]

After replacing the stat, water pump, checking hoses and rads and multiple see saw filling carefully we have come to the conclusion bongo is creating air somewhere in the system. Which can only be either head gasket (hopefully) or the head itself.

The bubbles/boiling are rhythmic every 25 seconds getting closer the hotter the bongo gets, no amount of see sawing, squeezing pipes or flushing has stopped this.

We will possibly have the head hot pressure tested, we need to find a garage to do this, anyone have any experience with this!?

[Bob]

A rough location would help us to help you.

[Northern Bongolow]

if you go into any old school garage they will know the best people in your area to get it tested, or any garage can do you a test on the coolant that shows up the presence of exhaust gasses, do this first before presuming the worst. hope your lucky mate.

[Lordward]

We bit the bullet and dismantled, crack in the head gasket, water in number 3. Figuring hot testing, seals and other ancillary bits to put the original back together, for us to not trust it due to stresses it's been under, so we are considering a full replacement of the head.

We are in Middlesbrough. Any ideas for a good supplier?

[Northern Bongolow]

contact ian at bongo fury, he has a good source for the complete kit with a proven record, or you can try the mobile mechanic, i forget his name, he will travel to you and fit a head etc for a fixed price, someone will put up a link to his services.

[Long]

Hi Everyone,

i completed a full bleed of the bongo this weekend. with very helpful advice from ady. (thank you). this morning the coolant did drop about 1cm below the full mark as anticipated.

i haven't gone for a longer drive yet, but initially idle and short drive there has been no problems, even with the AC on. heater is give good heat. Hopefully my problem is fixed will go for longer drive to test.

will keep update. thanks

[Long]

Hi, everyone,

i completed another successful test drive with the bongo not over heating. during the test i noticed a couple of thing i wanted to ask and see if they were normal.

1. when driving (AC on) the level in the header tank is at about 1CM above the full mark. when idle 1-2mm above full
2.i went for a short drive and bongo got to operating temp, but the lower rad hose was still cool. i didn't drive it very fast 25-30kmph at most
3.i drove it more and faster and the lower hose was warm at most. def not as hot as top hose. ( it was a cooler day) maybe it was not hot enough for thermostat to completely open? (when i was bleeding the system the bottom hose got very hot but the engine was on for a lot longer)

are the above normal running conditions?

thanks alot. will test again and see if it over heats.

[cmm303]

All sounds about right. Much as my bongo behaves.

Expansion tank level seems to be about 0.5-1cm above cold level when at working temp in the 85-90s.

Bottom hose will be cooler during gentle driving than stationary bleeding. Air flowing through the rad is cooling it more than the engine is heating it - a good condition - and the thermostat slows the flow to maintain a warm engine, thus cool/tepid bottom hose. When stationary (e.g. During bleeding) the coolant is not being cooled much in the rad so it comes out the bottom hose hotter. As the engine isn't cooled so much the stat will open more, increasing the flow. As it's not being cooled so much in the rad and the engine is getting hotter the bottom hose gets hot. Try bleeding with bongo facing into a cold wind - it can be difficult to get the bottom hose hot without blocking out the wind.

If factors during driving mean that the engine generates more heat than the rad is dissipating (e.g. towing up a long slow steep hill in steaming hot weather) then the bottom hose would be scorching. In this scenario eventually the rad fans come on to increase the effectiveness of the rad so hopefully it is cooling more heat than the engine is creating.

[Northern Bongolow]

sounds promising mate. take your time and get your confidence back, then take it out and give it a dam good thrashing, basil faulty style.

https://www.youtube.com/watch?v=78b67l_yxUc

[cmm303]

The experts have relaxed

[Long]

Hi,

I went for another test drive. the bongo did well for 20-30 mins, then the level in the head tank was about 3 cm above full. I knew there was a problem. the bottom hose was still cool.

i drove it some more and it began to over heat. and coolant boil. i stopped the car right away and felt the bottom hose, it was still cool. I then went to feel the hose on the passenger side where the thermostat is, it was very hot on the top of the thermostat, and cool on the other side.

i am suspecting I have a faulty thermostat stuck closed? and not letting the coolant flow to the radiator causing the overheating. The thermostat must sometime open and sometimes not.

does this sound like the problem.

thanks

[teenmal]

Personally I would remove and test/renew the temperature control valve/thermostat , it might just be a coincidence that it has acted up after you carried out the previous work. You can actually check the cross flow in the radiator but unless you are confident with this procedure I would just test/renew.

How long have you had the vehicle?, if it is a recent purchase a Sniffer test might be in order.

This is presuming that All the Air has been removed from the system, any doubts I would go for a Vacuum drain and fill.

The Thermostat is the engine coolant temperature Control Valve.

Good Luck.